Some coating applications require relatively thick films. For example, coatings to be applied to substrates such as, for example, foamed-in-place polyurethane foam, used to insulate and protect industrial building roofs, are conventionally on the order of 10-40 mils (0.02-0.10 cm.) thick. Such coatings are frequently referred to as "roof mastics" although "mastic coatings" as used herein includes any such thick coating applied to either a vertical surface such as, for example, a wall, or to a substantially horizontal surface such as, for example, a roof deck. In some cases, the substrates to which it is desired to apply mastic coatings present problems such as, for example, difficulty in adhesion due to a deteriorated substrate surface or the presence of highly colored bodies in or on the substrate which may migrate into and discolor the mastic coating. The tiecoats of this invention, disposed between the substrate and the mastic coating, solve such problems without unduly complicating or hindering the overall objective, the application of an effective mastic coating system.